1. Field of the Invention
This invention relates to weldable structures such as metal joints, bends and brackets that are braced with gussets, specifically welded-on type gussets that improve the resistance of such structures to fatigue failure from vibration, and to an improved process for effecting the bracing.
2. Description of the Prior Art
The conventional welded-on metal gusset bracing a rigid angular joining between a pair of diverging metal surfaces against fatigue failure from vibration is transverse to (usually normal to) and on edge towards both such metal surfaces. Such "erect" or "plate-type" gusset is a triangle or trapezoid that typically fills in all or most of the angle between such surfaces where they intersect. Such gusset ordinarily is secured by boxing it with fillet weld beads, that is the beads are deposited all along the side edges and the far end edges of the gusset where it meets the metal surfaces being braced. The time required to so weld, for example, a mild steel trapezoidal gusset of this type that is approximately 5/16 inch thick, is about three inches long on its longest side, and reaches down to about one-half inch above the fillet-welded right angle joint between two steel members, is about three minutes using manually a gas metal arc weld (GMAW) method skillfully.
The instant process has as a principal virtue the speeding-up of the welding process considerably, and this without losing fatigue resistance of the resulting gusseted joint in comparison to the same joint having a conventional erect gusset of the same thickness and maximum span. Additionally, the amount of metal in the instant gusset structure for the same service can be less than that in the conventional event gusset while attaining essentially the same or better operating performance. Thus, the instant structure represents appreciable economy and speed of assembly, as well as simplicity and versatility of gusset design, manufacture, and attachment onto the structure.
The invention utilizes plug welds. A plug weld is a deposit of weld metal inside a hole (not necessarily circular in cross-section) that goes clear through one weldable metal piece and abuts another weldable metal piece. The weld connects the two pieces. Such welds often substantially fill the weld hole, but need not do so to be effective; a weld bead around the inner periphery at the base of the weld hole in one piece of metal where it abuts the other can be quite effective for many of the instant structures.
Plug welds in various configurations have been used heretofore to make connections between various metal pieces, to make elements for various construction units, and to make marine piling connections. However, to depart from the conventional erect gusset with its fillet welding attachment to the surfaces being braced, to employ a footed type between joined diverging surfaces, and to plugweld the feet in place to brace such surfaces against fatigue failure is believed novel as well as being surprisingly economic and effective.